Pumps generally include a cam that rotates relative to a housing. This rotation is used to impart forces upon fluids to then direct the fluids as desired. To allow rotation of the cam relative to the housing, there is some degree of freedom therebetween. In the case of cams, this freedom also provides the potential for the cam to move axially relative to the housing. Axial movement of the cam has the potential to impair the functionality of the pump and to cause wear on abutting surfaces. Certain forces, thrust forces, are experienced by the cam that urge such axial movement. Accordingly, designs are provided that minimize, counteract, and/or contain such thrust forces.
Effective control of thrust forces often includes the management of such thrust forces in both directions along the axis of rotation. Also, precise forming and sizing of the various parts is typically required so as to allow a small amount of axial movement of the cam without impairing the ability of the cam to rotate about the axis of rotation freely. Such precise forming and sizing can be costly and/or time consuming.
Accordingly, there exists a need for an improved method and apparatus that provides adequate thrust control while allowing easy assembly and while allowing variance in at least some of the part sizes.